Pregnancy is calculated from the first day of the woman's last period, so the first two weeks of pregnancy are actually the preconception weeks. During this time, the woman is probably not pregnant yet. During the 10 to 14 days following the first day of the woman's menstrual cycle, she will release an egg that goes down her fallopian tube. The egg then waits to be fertilized by the father's sperm. On average, women have a 20 percent chance of becoming pregnant during each cycle. Some women experience no symptoms at all, however, so if you don't experience any symptoms in this time period, it doesn't necessarily mean you're not pregnant.